Project Summary The near-elimination of HIV transmission with antiretroviral therapy (ART) has provided the world with a clear path to end the HIV epidemic through the mass provision of ART at diagnosis, i.e. test-and-treat. Despite the very large prevention benefits of ART, we found very limited knowledge of treatment-as-prevention (TasP) in two population-based surveys we recently conducted in South Africa (Bor K01). Indeed, current public health messaging and clinical HIV counseling in South Africa do not emphasize the prevention benefits of ART. In 2016, U=U Campaign was launched to disseminate the scientific evidence that people with HIV cannot transmit the virus if their viral load is undetectable. U=U has been endorsed by NIH and by organizations in nearly 100 countries. Anecdotal evidence suggests providing information on U=U may reduce stigma and improve wellbeing of PLWH, and may lead to increased ART uptake and adherence by appealing to the desire of PLWH to avoid transmission to others. Although the science on U=U is clear, there is currently a critical evidence gap on (a) how best to integrate information on U=U into HIV counseling services, and (b) what impact U=U messaging has on wellbeing of PLWH and on treatment-seeking behaviors. We propose a formative research study (R34) to develop an app-based educational video intervention that will provide information on U=U that is locally-appropriate and can be integrated into routine HIV counselling. We will pilot the intervention in a clinical trial of patients receiving HIV post-test and adherence counseling services, in order to determine feasibility and acceptability, impact on U=U knowledge and attitudes, impact on stigma and psychological wellbeing, and preliminary evidence for ART uptake, adherence, and viral monitoring and suppression. The study builds on a longstanding collaboration between Boston University and the Health Economics and Epidemiology Research Office (HE2RO) at the University of Witwatersrand in South Africa. This study is highly innovative because we take a novel approach ? disseminating information on the prevention benefits of ART ? to improve wellbeing of PLWH and motivate early uptake of ART in South Africa. Study results will inform an R01 proposal to evaluate the impact of this intervention on viral suppression in a cluster-randomized efficacy trial. The research will have significant public health impact as the findings have potential to shape HIV counseling guidelines and practice in the country with the world?s largest HIV epidemic. We hypothesize that selling treatment-as-prevention on its merits could substantially improve wellbeing of PLWH and increase demand for ART, enabling countries to maximize the impact of test-and-treat.